Region Filter

Overview

Selects regions by a condition such as ID, area, randomness, or edge contact. Unselected pixels become outside pixels. It can keep only large islands, remove regions that touch an edge, or randomly thin regions into a pattern while preserving the RegionMap type.

• Category: Generate / Region / Select
• Uses: keeping only small regions, removing edge-touching regions, and randomly thinning regions

Usage tips

• Random thinning is visually useful: thin Voronoi regions into scattered stones, or noise islands into isolated shrubs.
• Think of it as the Region counterpart to list_filter, retaining elements that meet a condition.
• The output remains a RegionMap, so fill, boundary, and distance nodes work downstream. If you only need a black-and-white mask, region_mask is more direct.

Related nodes

• region_mask — extracts the result as a mask image
• region_neighbor_select — selects by adjacency
• region_grow_shrink — fills outside pixels after filtering
• region_merge_small — merges regions instead of removing them

Modes

How to use

Connect nodes such as Region Cells.regions -> Region Filter.regions -> Region Fill.regions.

To remove regions that are too small, set mode = AreaRange and raise min_area. To remove edge-touching regions, use mode = EdgeTouch with invert = true.

When the input RegionMap wraps horizontally or vertically, edges in that direction connect to the opposite side instead of outside. In a tile that wraps both ways, a region is not treated as EdgeTouch merely because it lies at an edge.

Enable compact_ids only when needed. It is off by default so the original IDs remain aligned with upstream selections.

Region Mask differs in its output type. Region Filter returns the selection as a RegionMap, allowing further use of Region Fill, Region Border, Region Distance, and other region nodes. Use Region Mask when you need only a regular image mask.